Physiology Flashcards
What is an intrinsic control system?
System to maintain homeostasis within an organ
What is an extrinsic control system?
A system to control homeostasis initiated outside an organ
What is a feedforeward system?
A response in anticipation to a change
What does positive feedback do?
A response after a change that amplifies that change (ie contractions in labour)
What does negative feedback do?
A response that occurs after a change that opposes the initial change
What is blood pressure?
The outwards pressure by the blood on the vessel walls
What is systolic BP a measure of?
Pressure excerted during heart contraction
What is diastolic BP a measure of?
Pressure excerted when the heart relaxes (dia-dies)
What is pulse pressure?
Systolic - diastolic
What is a normal systolic and diastolic?
Systolic <140mmHg at rest
Diastolic <90mmHg at rest
What is a normal pulse pressure?
30-50mmHg
What is the mean arterial BP?
The average pressure over 1 cardiac cycle
How do you calculate the MAP?
[(2×diastolic) + systole] ÷ 3
What is the normal range for MAP?
70-105mmHg
What is the minimum MAP needed to peruse vital organs?
60mmHg
How else can you calculate the MAP (apart from using systole and diastole)?
MAP = CO × SVR
MAP = SV × HR × SVR
How do you calculate the cardiac output?
CO = SV × HR
What is the cardiac output?
The volume of blood pumped per ventricle per minute
What is the stroke volume?
Volume of blood pumped by each ventricle per heart beat
What can you alter to control blood pressure?
Stroke volume
The heart rate
The systemic resistance
Which part of the nervous system controls the heart rate?
The autonomic nervous system
What part of the ANS increases the heart rate?
Sympathetic
What effect does the parasympathetic division of the ANS have on heart rate?
The division of the vagus nerve decreases heart rate
Does vasoconstriction increase or decrease SVR and MAP?
Increase
How can heat be exchanged to the external environment?
Radiation
Evaporation
Conduction
Convection - forced air movement
What do tight junctions do?
Join the lateral edges of epithelial cells near their apical membranes
What do desmosomes (anchoring junctions) do?
Link adjacent cells tightly to provide mechanical strength
What do gap (communicating) junctions do?
Allow the movement of ions and molecules between adjacent cells
What 5 factors influence diffusion across the membrane?
The magnitude of the concentration gradient
The surface area of the membrane
The lipid solubility of the substance
The molecular weight of the substance
The distance through which diffusion is taking place
What is tonicity?
The effect a solution has on cell volume
Can be iso- hypo- or hyper-
What does isotonic mean?
There is no movement of water, therefore no change in cell volume
What does hypotonic mean?
Water moves into the cells causing them to swell.
What does hypertonic mean?
Water moves out of the cell, causing the cell to shrink
What does the sodium, potassium ion pump do?
Helps to establish sodium and potassium in concentration gradients
For every 3 Na+ out 2K+ go in
What are the two types of vesticular transport and do they require energy?
Exocytosis
Endocytosis
Yes - active process
What is the membrane potential?
The separation of opposite charges across the membrane due to differences in the concentrations and permeability of ions
Which cells produce action potentials when they are excited?
Nerve and muscle cells
Is the concentration for K+ ions outwards or inwards?
Outwards
If the permeability of Na+ ions is increased across a cell membrane what happens to the membrane potential?
It is driven closer towards the Na+ ions equilibrium potential. So the membrane potential is increased
What is the resting membrane potential?
-70mV
What is the equilibrium potential for K+ ions?
-90mv
What is the Nernst equation and what is it used for?
Eion = 61log10 [ion]outside/[ion] inside
Used to calculate the equilibrium potential for any given ion
what is the equilibrium potential for sodium ions?
+61mV
What formula is used to calculate the resting membrane potential?
the goldman-hodgkin-katz equation
what happens during depolarization?
the membrane potential becomes less negative
what happens during hyperpolarization?
when the membrane potential becomes more negative
what happens during repolarisation?
the depolarised state returns back to the normal resting value
Passive movement of an ion through an ion channel is driven by…
the electrochemical gradient for that ion
Why do sodium ions flow inwardly?
the concentration gradient is inward
the electrical gradient is inwards
why do potassium ions flow outwardly?
because the concentration gradient is outwards and the energy of that exceeds that of the electrical gradient which is inwards
if lots of sodium ion channels are open, what effect does this have in the membrane potential?
it increases towards the equilibrium potential for the sodium ions
what can ion channels be gated by?
LGICs
VGICs
Physical stimuli - for example mechanical stretch
which type of ion gated channel is responsible for the action potential in neurons?
VGICs
what is an action potential?
An all or nothing, brief electrical signal in which the polarity of the membrane is momentarily reversed
when are action potentials generated?
when the threshold is reached
what is the upstroke in an action potential caused by?
the opening of sodium ion channels - causing depolarization
what is the downstroke caused by?
the opening of potassium ion channels and the inactivation of sodium ion channels
what is the undershoot caused by?
the delayed closure of the voltage activated potassium ion channels
what 3 states do voltage gated sodium ion channels exist in?
closed
open
inactivated
what is needed for the sodium ion channels to return to its closed state?
repolarisation
how can you increase passive current speed in a nerve fibre?
increasing the diameter of the axon
or
add an insulating material (myelin) to decrease the leak of current across the axon
How are impulses sent in myelinated axons?
by saltatory conduction - the signal jumps from one node of Ranvier to the next
what happens to the action potential in un-myelinated axons?
there is a passive (leaky) spread of current
what are the pre and postganglionic neurotransmitters in the parasympathetic division?
Acetyl choline for both
what are the pre and postganglionic neurotransmitters for the sympathetic division?
pre = acetyl choline
post = noradrenaline
how is a neurotransmitter’s release via exocytosis induced?
by calcium ion influx through voltage activated calcium channels
